1. Field of the Invention
The present invention relates to a method of manufacturing a resin multilayer substrate.
2. Description of the Related Art
A resin multilayer substrate having a rigid portion and a flexible portion is known. Such a resin multilayer substrate consists of a flexible portion (a portion that is thinner or has fewer layers and higher flexibility) and a rigid portion (a portion that is thicker or has more layers and lower flexibility). The rigid portion is different from the flexible portion in a number of insulation substrates or in a composition material of the insulation substrate. Furthermore, as a method of manufacturing a resin multilayer substrate, there is a known method by which resin sheets, each made of a thermoplastic resin and having a conductor pattern formed thereon are stacked, then heated and pressurized by a heat pressing plate, and collectively bonded as a stacked body.
Japanese Patent Laying-Open No. 2003-264369 discloses a method of manufacturing a via-filled single-sided conductor pattern film. The method includes the steps of: affixing a PET film to a single-sided conductor (Cu) pattern resin film; providing a via hole by a laser beam from the PET film side and charging an interlayer connection material (via paste); and making a cut in a boundary between a rigid portion and a flexible portion, in which the cut is made in a length equal to or greater than the width of a product.
In Japanese Patent Laying-Open No. 2003-264369, however, a cut for forming a cavity is made after via paste is charged. Accordingly, due to vibration caused by cutting and conveyance, the via conductor tends to spatter or fall off, which leads to short-circuit defects or electric connection failures in a via. It is to be noted that this manufacturing method does not allow a film (for example, a PET film) functioning as a mask for via filling to be conveyed in the state where this film is held as a carrier film.
In addition, Japanese Patent Laying-Open No. 2005-322838 discloses a method of manufacturing a flexible wiring substrate equipped with a stiffening plate. In this manufacturing method, the surface side (pattern side) of the flexible wiring plate is affixed to a slightly adhesive film, and the flexible wiring plate is half-cut from its back surface side while using the slightly adhesive film as a carrier, thereby cutting the flexible wiring plate in a prescribed shape without cutting the slightly adhesive film. However, Japanese Patent Laying-Open No. 2005-322838 does not describe a manufacturing method of performing via filling, and also does not provide a carrier film functioning as a mask for via filling.